Air heater systems and control methods

ABSTRACT

A method for controlling an air heating system is disclosed with an air chamber, an inlet, an outlet, wherein the outlet may be positioned closer to the floor of the room than the inlet, a fan for motivating air to pass from the room to the air chamber and back into the room, an inlet temperature sensor, an outlet temperature sensor, a room temperature sensor, and a controller, the controller to control fan speed based on the temperatures sensed.

BACKGROUND

1. Technical Field

The present disclosure relates air heater systems and control methods therefore.

2. Description of the Related Art

Air heaters systems in the related art include an air chamber with at least one inlet and at least one outlet, both coupling the air chamber to a room, the room containing air to be heated. Air from the room enters the air chamber at the inlet, is heated by heat transfer from surroundings of the air chamber or by mixing with pre-heated air resident in the air chamber, and then exits the air chamber by the outlet, into the room.

Air heaters include solar air heaters. Solar air heaters may be located external to a home, room or other structure containing air to be heated. Positioning the air chamber external to the room allows the air chamber to be heated through thermal contact with the external air, or by interception of incident solar radiation.

In such arrangements, air from the room enters the inlet. The inlet passes through the wall of the home to the external air chamber. When the air in the external air chamber is at a higher temperature than the air entering at the inlet, then the air entering will be heated, and the air exiting at the outlet will be at a temperature greater than that entering at the inlet, thus heating the air in the room.

Solar air heaters in the art are generally arranged so that the inlet is positioned towards the bottom of the air chamber, towards the floor of the room. The outlet is generally positioned towards the top of the air chamber, towards the ceiling of the room. Cool air may enter the inlet under convection or under the motive force of a fan. The air may be heated in the air chamber. Warmer air is less dense than cooler air. The air in the air chamber will rise as it is heated, and may push warmer air out of the outlet and may draw cooler air in at the inlet.

In such systems, a simple control system may be employed to sense when the outlet temperature is greater than the inlet temperature and to allow the flow of air at that point.

However, exhausting warm air at the outlet, at the top of the air chamber, towards the ceiling of the room, is not desirable as it may reinforce a thermal gradient within the room with colder air towards the floor, and warmer air towards the ceiling. This thermal gradient may not be desirable for the occupants of the room.

It is advantageous to have warm air exit towards the floor of the room rather than at the ceiling. Such a system would be novel and would help to reduce the thermal gradient within the room. Such a system would also require a novel control method.

BRIEF SUMMARY

A method for controlling an air heating system is disclosed. In one embodiment, the air heating system is adapted for heating air in a room, the air heating system comprises an air chamber, an inlet coupling the room to the air chamber to allow the passage of air from the room into the air chamber, an outlet coupling the air chamber to the room to allow the passage of air from the air chamber to the room, a fan for motivating air to pass from the room to the air chamber and back into the room, an inlet temperature sensor which yields an inlet temperature value, an outlet temperature sensor which yields an outlet temperature value, a room temperature sensor which yields a room temperature value, and a controller, the controller having data storage for storage of a minimum fan speed value, a fan start threshold value, a fan timer value, a temperature gradient value, a full fan speed value, and a maximum fan speed value, wherein the controller is adapted to control speed of the fan, the method comprising: determining if the inlet temperature value is greater than the fan start threshold value, and if so setting the fan to run for the duration of the fan timer value at at least the minimum fan speed.

In another embodiment, the controller data storage stores a temperature gradient value, and the method further comprises determining if the outlet temperature value is greater than the room temperature and if so, further determining if the outlet temperature value is greater than the inlet temperature value by the temperature gradient value, and if so, setting the fan to run at a speed dependent on the outlet temperature value, greater than or equal to the minimum fan speed value and less than the maximum fan speed value.

In another embodiment, the controller data storage further stores a fan acceleration value and the method further comprises determining if the actual fan speed is less than the desired fan speed and if not, then setting the actual fan speed to the desired fan speed and reducing the fan acceleration value, and if the actual fan speed is less than the desired fan speed, increasing the actual fan speed by the fan acceleration value and if the actual fan speed then is equal to the desired fan speed, then increasing the fan acceleration value.

In another embodiment, the method further comprises determining if the outlet temperature value is greater than or equal to the full fan speed value and if so, setting the fan to run at the maximum fan speed value.

In another embodiment, if the fan timer value is exceeded, and if the outlet temperature value is not greater than the inlet temperature value by the temperature gradient value, then the method further comprises shutting down the fan.

In another embodiment, an air heating system for heating air in a room is disclosed, the air heating system comprising an air chamber, an inlet coupling the room to the air chamber to allow the passage of air from the room into the air chamber, an outlet coupling the air chamber to the room to allow the passage of air from the air chamber to the room, a variable speed fan for motivating air to pass from the room to the air chamber and back into the room, an inlet temperature sensor which yields an inlet temperature value, an outlet temperature sensor which yields an outlet temperature value, a room temperature sensor which yields a room temperature value, and a controller for controlling the speed of the fan wherein the controller is adapted to control the speed of the fan based on at least one of the inlet temperature value, the outlet temperature value, and the room temperature value.

In one or more of the above embodiments, the room comprises a floor and a ceiling and the air heating system is configured such that the outlet is positioned closer to the floor than the inlet.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

FIG. 1A is a schematic diagram of a side view of an air heating system according to one embodiment.

FIG. 1B is a schematic diagram of a side view an air heating system with two air chambers, according to one embodiment.

FIG. 2 is a flow chart of the steps of the calculation of the desired fan speed according to one embodiment.

FIG. 3 is a flow chart of the steps of the setting of the actual fan speed according to one embodiment.

FIG. 4 is a schematic of a controller for controlling one air heater, according to one embodiment.

FIG. 5 is a schematic of a controller for controlling two air heaters, according to one embodiment.

FIG. 6 is a schematic of a controller for controlling two air heaters, according to another embodiment.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known materials, structures and methods associated with transmissions have not been shown or described in detail, to avoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

FIG. 1A is a schematic diagram of an air heating system 10 for heating air (not shown) in a room 14, having a floor 15A and a ceiling 15B, the air heating system 10 includes an air chamber 16, an inlet 18 coupling the air chamber 16 to the room 14 to allow the passage of air from the room 14 into the air chamber 16, an outlet 20 coupling the air chamber 16 to the room 14 to allow the passage of air from the air chamber 16 to the room 14. A fan 22 is located to motivate air (not shown) to pass from the air chamber 16 to the room 14 via the outlet 20 and from the room 14 into the air chamber 16 via the inlet 18.

The fan 22 may be a conventional bladed fan and may include such commercially available fans such as a computer case fan and may also include a fan such as direct current fan model AFC0912D-AFOO available from Delta Electronics Inc., 252, Shang Ying Road, Kuei San Industrial Zone, Taoyuan Shien, Taiwan. The fan 22 need not be a rotational fan and may be a bladeless fan or air multiplier. Fan 22 need not be located in the outlet 20 as shown in FIG. 1A. Fan 22 may be located anywhere so as to impart a motive force to air so that air moves from the room 14 through the inlet 18 into the air chamber 16 and from the air chamber 16 through the outlet 20 to the room 14.

An inlet temperature sensor 24 is positioned to sense the temperature at or near the inlet 18 to yield an inlet temperature value. An outlet temperature sensor 26 is positioned to sense the temperature of the air (not shown) at the outlet 20 to yield an outlet temperature value. A room temperature sensor 28 is positioned to sense the temperature of the air (not shown) at or near the room 14 to yield a room temperature value.

Air chamber may have one or more inlets and may have one or more outlets. A person of ordinary skill in the art could determine the appropriate number of inlets or outlets for a particular application and configure the controller to control one or more fans associated with such a configuration.

The air heating system may further include a heat bath chamber thermally connected to the air chamber. The heat bath may be exposed to the incident solar radiation and may be thermally connected to the outside of the room. Thermal energy captured or transferred to the heat bath may then be transferred to the air in the air chamber. Air chamber may reside within heat bath, so as to maximize thermal contact, but may not be in fluid communication with heat bath. Air chamber may include baffles, or turbulence inducing elements to vary the flow of air within air chamber to maximize resident time of air within air chamber or to ensure flow of air within a greater portion of air chamber to increase thermal exchange of thermal energy to air. The arrangement or inclusion of air chamber, heat bath, baffles, turbulence inducing elements, or other aspects of the air chamber may be selected by a person of ordinary skill in the art and should not be read as limiting the scope of this disclosure.

The inlet temperature sensor 24 need not be placed directly within the inlet 18. The inlet temperature sensor 24 need only sense the temperature at or near the inlet 18. The outlet temperature sensor 26 need not be placed directly within the outlet 20. The outlet temperature sensor 26 need only sense the temperature at or near the outlet 20. The room temperature sensor 28 need not be placed directly within the room 14 or at any specific location in the room 14. The room temperature sensor 28 need only sense the temperature at or near the room 14. The room temperature sensor 28 may be located within an enclosure, the enclosure may also enclose a controller 32, or room temperature sensor may be located outside such an enclosure and may be proximate or not proximate to controller 32. Each of the inlet temperature sensor 24, outlet temperature sensor 26, and room temperature sensor 28, may be any temperature measuring device, including but not limited to analogue and digital measuring devices, thermistors, thermocouples, integrated circuit thermometers and resistance temperature detectors. An example of a suitable thermistor is model number NTCLE100E3332JB0 available from Vishay BCComponents, Vishay Americas, One Greenwich Place, Shelton, Conn., 06484, United States.

The values yielded by each of the inlet temperature sensor 24, outlet temperature sensor 26, and room temperature sensor 28, the inlet temperature value, outlet temperature value, and room temperature value, need not be values that directly correspond to a temperature number as measured in degrees on a temperature scale, such as the Celsius, Fahrenheit or Kelvin scales, for example. Rather, the values need only be usable by controller 32 for comparison to other values, and may include offsets, or different rates of value change over temperature change, depending on the type and model of temperature sensor used.

Controller 32 is informationally connected to each of the inlet temperature sensor 24, outlet temperature sensor 26, room temperature sensor 28, to sense the inlet temperature value, outlet temperature value, the room temperature value and is further informationally connected to the fan 22 to control the actual speed of the fan 22. The connection between controller 32 and each of the inlet temperature sensor 24, outlet temperature sensor 26, room temperature sensor 28, and to the fan 22, may be by any means selected by a person of ordinary skill in the art including by wire, wireless, digital, analogue, optical, or other means.

The controller 32 is adapted to hold certain values including the minimum fan speed value, fan start threshold value, a fan timer value, a temperature gradient value, a full fan speed value, and a maximum fan speed value that may be used in determining when to start, stop, speed up, or slow down the actual speed of the fan 22, where the actual fan speed is limited to the maximum fan speed value, the maximum fan speed value representing the maximum speed at which the fan is permitted to run. Each of these values may be hard coded, or may be a value programmed into the controller 32, based on local conditions, and the fan acceleration value may be adjusted during operation based on the processes described below.

Based on the information provided by each of the inlet temperature sensor 24, outlet temperature sensor 26, and room temperature sensor 28, the controller 32 will determine the desired speed of the fan 22. The algorithm for determining the desired value of the speed of fan 22 is described below.

Controller 32 will also adjust the actual speed of the fan 22 based on the desired speed of the fan 22. As is described more fully below, the actual speed of the fan 22 may not always match the desired speed of the fan 22 and the rate of change of the actual speed of the fan 22 may not be constant, but may be adjusted based on values stored by controller 32.

In operation, incident radiation will heat the air chamber 16 which will in turn heat air resident in air chamber 16. Warmer air will rise towards the inlet 18 and the inlet temperature sensor 24 will respond to an increase in the inlet temperature value. The controller 32 will sense each of the inlet temperature value, outlet temperature value and room temperature value.

In most cases, in the configuration where the outlet 20 is positioned closer to the floor 15A than the inlet 18, and where the inlet 18 is positioned closer to the ceiling 15B than the outlet 20, prior to operation of the fan 22, the temperature sensed at the inlet temperature sensor 24 will be higher than the temperature sensed at the outlet temperature sensor 26, due to the air in the air chamber 16 being heated by incident radiation and rising within the air chamber 16 towards the inlet 18 and the inlet temperature sensor 24.

The operation of fan 22 is governed by controller 32. Controller 32 will calculate the desired fan speed and will control the actual fan speed based on the desired fan speed however, controller 32 also includes for the fan 22 to run for a period of time based on the fan timer value, as is described below.

FIG. 1B is a schematic diagram of an air heating system with two air chambers, according to one embodiment. The air heating system with two air chambers may have an inlet associated with each air chamber, an outlet associated with each air chamber and a fan associated with each air chamber. The air heating system with two air chambers may have a separate inlet temperature sensor for each inlet, a separate outlet temperature sensor for each outlet and may have a separate room temperature sensor associated with each air chamber, where the two air chambers are associated with two different rooms, for example or may have a common room temperature sensor serving both air chambers, where the two air chambers are associated with a single room, for example.

In FIG. 1B, air heating system 10 for heating air (not shown) in a room 14 having a floor 15A and a ceiling 15B, the air heating system 10 includes a first air chamber 16, and a second air chamber 16B, a first inlet 18 coupling the first air chamber 16 to the room 14 to allow the passage of air from the room 14 into the first air chamber 16, and a second inlet 18B coupling the second air chamber 16B to the room 14 to allow the passage of air from the room 14 into the second air chamber 16B, a first outlet 20 coupling the first air chamber 16 to the room 14 to allow the passage of air from the first air chamber 16 to the room 14, and a second outlet 20B coupling the second air chamber 16B to the room 14 to allow the passage of air from the second air chamber 16B to the room 14. A first fan 22 is located to motivate air (not shown) to pass from the first air chamber 16 to the room 14 via the first outlet 20 and from the room 14 into first the air chamber 16 via the first inlet 18. A second fan 22B is located to motivate air (not shown) to pass from the second air chamber 16B to the room 14 via the second outlet 20B and from the room 14 into the second air chamber 16B via the second inlet 18B.

A first inlet temperature sensor 24 is positioned to sense the temperature at or near the first inlet 18 to yield a first inlet temperature value. A first outlet temperature sensor 26 is positioned to sense the temperature of the air (not shown) at or near the first outlet 20 to yield a first outlet temperature value.

A second inlet temperature sensor 24B is positioned to sense the temperature at or near the second inlet 18B to yield a second inlet temperature value. A second outlet temperature sensor 26B is positioned to sense the temperature of the air (not shown) at or near the second outlet 20B to yield a second outlet temperature value.

A room temperature sensor 28 is positioned to sense the temperature of the air (not shown) at or near the room 14 to yield a room temperature value. The two air chamber air heating system may share a room temperature sensor 28, as is depicted in FIG. 1B, or there may be a separate room temperature sensor, one associated with each air chamber. As would be apparent to a person of ordinary skill in the art, a separate room temperature sensor may be preferred if the air chambers 16 and 16B are located in different parts of a large room, or if the air chambers 16 and 16B are located in different rooms. That is, although FIG. 1B depicts the air chambers 16 and 16B being located in the same room, this is not intended to limit the scope of the invention and air chambers 16 and 16B may be located in different rooms.

FIG. 2 is a flow chart of the steps of the calculation of a desired fan speed, and for operating the fan 22 on the basis of the fan timer value, according to one embodiment. The controller 32 may conduct the steps outlined at a clock interval of controller 32. For example, at each clock interval of controller 32, the steps described in FIG. 2 and FIG. 3, both described below, may be undertaken. As such, the controller 32 may repeat this analysis at each clock interval of controller 32.

FIG. 2 starts the process at step 200, the initiation of the process. The first active step of the process at FIG. 2 is step 205 where controller 32 will determine whether the inlet temperature value is greater than a fan start threshold value. If the inlet temperature value is greater than the fan start threshold value, it is an indication that the air in the air chamber 16 is sufficiently warm to start the fan 22. If so, at step 245, controller 32 will determine whether the fan timer is already running down from the fan timer value, for example, from a previous iteration of the process in FIG. 2. If the fan timer is not already running down then, at step 265, controller 32 will set the desired fan speed to a minimum fan speed value. Controller 32 does not yet set the fan 22 running, it simply sets the desired fan speed to the minimum fan speed value at step 265. At step 270, controller 32 will set the fan timer to start running for the duration of the fan timer value. Next, at step 275, controller 32 will determine if the fan 22 is actually running for example, from a command from controller 32 at a previous iteration of the processes described herein. If not, at step 280, controller 32 will set the actual fan speed to the minimum fan speed, which at this point is the desired fan speed. Controller 32 then proceeds to step 210.

If controller 32 determines at step 205 that the inlet temperature is not greater than the fan start threshold value, then controller 32 will proceed to step 210.

If controller 32 determines at step 245 that the fan timer value is already set, then controller 32 will bypass steps 265, 270, 275 and possibly 280 and go to step 210, as that indicates the process set by steps 265, 270, 275 and possibly 280 had occurred at a previous iteration.

If controller 32 determines at step 275 that the fan 22 is already running, then it will bypass step 280 and go to step 210.

While the fan 22 is running, the warmer air from the upper portions of the air chamber 16 will be motivated towards the lower outlet 20. The air at the outlet 20 will increase in temperature and that increase will be sensed by the outlet temperature sensor 26 and will yield a higher outlet temperature value.

At step 210, the controller 32 will determine whether the outlet temperature value is greater than the room temperature value. If not, then at step 230, controller 32 will determine if the fan timer has run down to zero from the fan timer value and if not, will complete the process at step 240 and will restart the process at step 200, the next time step of the controller 32. If at step 230 the fan timer is still running, and has not reached zero, then at step 235, controller 32 will set the desired fan speed to zero and will complete the process at step 240. In such a case, the fan timer duration may have been insufficient to kick start the conditions into sustained operation, given the particular conditions at the time.

If at step 210, the outlet temperature value is greater than the room temperature value, then at step 215, controller 32 will next determine whether the outlet temperature value is greater than the inlet temperature value, by the temperature gradient value. If not, then the controller 32 will proceed to step 230 as described earlier.

If at step 215 the outlet temperature value is greater than the inlet temperature value, by the temperature gradient value, then controller 32 will next determine at step 220 whether the outlet temperature value is at or above a full fan speed value. If not, then the controller 32 will proceed to step 225 and controller 32 will set the desired fan speed to be the result of a calculation. The calculation may set the desired fan speed to be between zero and the maximum fan speed value and may, within that bound set the desired fan speed to be dependant on the outlet temperature value. Controller 32 may set the dependency to be direct or based on some other function or relationship. After controller 32 calculates and sets the desired fan speed at step 225, at step 255, controller 32 will determine if the fan timer still has a non-zero value.

If at step 255 the fan timer is run down to zero then the controller 32 will proceed to step 240. If at step 255 fan timer has not yet run down to zero, is greater than zero, then at step 260, controller 32 will determine if the desired fan speed is greater than the actual fan speed. If so, controller 32 will proceed to step 285 and will clear the fan timer to zero and will proceed to step 240 and finish. If not, controller 32 will not proceed to step 285 and will not clear the fan timer to zero, but will proceed to step 240 and finish.

If at step 220, the outlet temperature value is greater than the full fan speed value, then controller 32 will proceed to step 250 and at step 250, controller 32 will set the desired fan speed to the maximum fan speed value. The maximum fan speed value means the fan 22 will run at 100% speed or at a preconfigured maximum speed once the outlet temperature value has exceeded the full fan speed value. That is, the full fan speed value is a preconfigured number to which the outlet temperature value is compared. When the outlet temperature value is greater than the full fan speed value, then this indicates that the fan should be run at its greatest output, and controller 32 sets the desired fan speed to the maximum fan speed. Controller 32 will then proceed to step 240 and finish.

The process in FIG. 2 will be repeated at each time step of controller 32. Once fan 22 is running where the fan timer has been cleared, then the fan 22 will continue to run until the outlet temperature is not greater than the inlet temperature value by the temperature gradient value at step 215, or the outlet temperature is not greater than the room temperature value at step 210.

The fan timer value allows the system to run for a period of time when the outlet temperature value is not greater than the inlet temperature value by the temperature gradient amount, and when the outlet temperature value is not greater than the room temperature value. During this time, the fan 22 will run counter to the thermal buoyancy force and will set up an opposite flow of air. If the incident radiation on the air chamber 16 is sufficient, along with the flow of air from the fan 22, to get the outlet temperature value sufficiently high, then the system will sustain running beyond the minimum fan timed session until the incident radiation is insufficient to maintain these conditions.

Once controller 32 sets the desired fan speed, a separate process is undertaken to control the fan speed. That is, the fan speed may not be immediately set to the desired fan speed once a new desired fan speed is calculated.

FIG. 3 is a flow chart of the steps of the control of the fan speed according to one embodiment.

The control fan speed process begins at step 300, which is a start step. At step 305, an optional hardware error checking step may be employed and if a hardware error is detected, the controller 32 proceeds to step 350 and switches off the fan 22 and proceeds to step 345, and finishes the process. If there are no hardware errors, then controller 32 proceeds to step 310.

At step 310 controller 32 checks to see if the desired fan speed is zero, resultant from the process described at FIG. 2. If so, then the controller 32 will switch off the fan 22 at step 350 and proceeds to step 345, and finishes the process.

If the desired fan speed is not zero, then controller 32 will proceed to step 315. At step 315, controller 32 determines if the actual fan speed is less than the minimum fan speed value. This step may also be optional, as it is an error handling step as this situation should not occur. If the actual fan speed is less than the minimum fan speed, then controller 32 proceeds to step 320, and at step 320, controller 32 will set the fan speed to the minimum fan speed value and will proceed to step 325. If the actual fan speed is not less than the minimum fan speed, then controller 32 will proceed directly to step 325.

At step 325, controller 32 compares the actual fan speed to the desired fan speed. If the actual fan speed is less than the desired fan speed, then the fan speed is too slow, and the controller 32 will proceed to step 330. At step 330, controller 32 will increase the actual fan speed by an incremental value, the fan acceleration value, which may be expressed as a fraction of the maximum fan speed per unit time. For example, the fan acceleration value may be a fraction less than 1 of the maximum fan speed value per second, such that the actual fan speed will increase at the fan acceleration value at each iteration of the controller 32, when controller 32 will make the next analysis as described herein. That is, the fan acceleration value is a value of speed, as measured in revolutions per minute or other suitable unit, which is added to the actual fan speed at each iteration of controller 32 and is not a rate of change of speed over time between iterations of controller 32.

The fan acceleration value will have a minimum value and a maximum value but may be adjusted by the controller 32 through the process described herein. After controller 32 increases the actual fan speed by the fan acceleration value at step 330, then the controller 32 will proceed to step 335. At step 335, controller 32 will determine if the actual fan speed is equal to the desired fan speed. If so, then the controller 32 will proceed to step 340 and will increase the fan acceleration value by an incremental value, up to the maximum value of the fan acceleration value. If the actual fan speed is not equal to the desired fan speed, then the controller 32 will proceed to step 345 and will complete the process.

If at step 325, the actual fan speed is not less than the desired fan speed, then the fan speed is too fast, and the controller 32 will proceed to step 355. At step 355, controller 32 will set the fan speed directly to the desired fan speed. Controller 32 will then proceed to step 360 where it will decrease the fan acceleration value by one increment, to no less than a minimum fan acceleration value. After setting the fan acceleration value, the controller 32 will proceed to step 345 and complete the process.

Controller 32 will repeat the process at FIG. 3 at the clock interval of controller 32 and in so doing, at each instance, the fan speed will be compared to the desired fan speed and the fan speed will be adjusted and the fan acceleration value may be adjusted. As the fan acceleration value changes through the process at FIG. 3, the rate of change of fan speed for each iteration may also change.

When the desired fan speed is greater than the actual fan speed, the actual fan speed will be increased by the fan acceleration value. That is, when the desired fan speed is greater than the actual fan speed, the actual fan speed may not be set immediately to the desired fan speed, but will be incrementally increased by the fan acceleration value at each iteration of the process. Conversely however, if the desired fan speed is less than the actual fan speed, the actual fan speed will be dropped to the desired fan speed in a single iteration.

If controller 32 proceeds to step 340, it may be indicative of a potential warming trend. As a warming trend may be present, it may be advantageous to get the fan 22 up to the desired fan speed faster at the next iteration, to take advantage of the increased thermal energy in air chamber 16, hence the increase of the fan acceleration value at step 340.

Similarly, if controller 32 proceeds to step 355 and step 360, then it may be indicative of a potential cooling trend and the fan acceleration value is reduced so that at the next time controller 32 proceeds to step 330, it will not speed up the actual fan speed by as large a fan acceleration value as the previous iteration. That is, after a cooling trend, the fan speed will build up more slowly than it did prior to the cooling trend.

The comparison of values in controller 32 may not be a direct value for value comparison, but may be completed based on an algorithm, if the units of the two values are different or if the value of one or more are offset by a specific constant, for example. In one embodiment, controller 32 may conduct analogue to digital conversions of the voltages reported and may use such values, which may range between 0 and 1023, for example, for comparisons or calculations.

Controller 32 may be programmed into a computer, may be a smart phone app, or may be comprised of an integrated circuit chip with associated wiring.

In one embodiment, controller 32 is comprised of a circuit board with a PIC16F1826 microcontroller, commercially available from Microchip Technology Inc., 2355 West Chandler Blvd., Chandler, Ariz., USA 85224-6199. In another embodiment, controller 32 may control a system with two independent air chambers as depicted in FIG. 1B (where each air chamber either shares a room temperature sensor or has a separate room temperature sensor associated with it), controller 32 may be comprised of a circuit board with a PIC16F1827 microcontroller, also commercially available from Microchip Technology Inc., 2355 West Chandler Blvd., Chandler, Ariz., USA 85224-6199. The microcontroller may monitor the temperature sensors by way of voltage divider input converted from analogue to digital signal and may similarly monitor the actual fan speeds and provide power to the fan 22 and control the actual fan speed by way of pulse width modulation (“PWM”) to fan 22. In an embodiment with two air chambers, controller 32 may also provide power to the fan 22B and control the actual fan speed of fan 22B by way of pulse width modulation to fan 22B.

In the above description, certain values are compared against another value. For example, in the description above, it is stated that at step 200, the controller 32 determines if the outlet temperature value is greater than the full fan speed value, and if so, then controller 32 will proceed to step 250. The above description should not be read as limiting such a determination to a pure determination if one value is greater than another. The values may be offset by a constant, or may rise at different rates, depending on the model of thermistor, or other measuring device, for example. Such constant offsets, different rates of voltage increase generated for different rates of temperature rises may be considered such that the associated decision to proceed to a step or not proceed to a step may not be a simple comparison to determine whether one numerical value is greater than another. Further, it should not be limiting that the comparison is referenced as a greater than comparison when a greater or equal to comparison may yield substantially the same macroscopic performance of the system. FIG. 4 is a schematic of controller 32 for the control of a single air chamber system. Pinouts for the PIC16F1826 microcontroller for the control of a single air chamber system as shown in FIG. 4 are:

Pin Name Analog or Digital Direction Connection 17 RA0 Digital Output LED status indicator 18 RA1 Analog Input Inlet temperature sensor 1 RA2 Analog Input Outlet temperature sensor 2 RA3 Analog Input Room temperature sensor 3 RA4 4 RA5 15 RA6 16 RA7 6 RB0 Digital Output Fan power on/off 7 RB1 Reserved for USART 8 RB2 Digital Output USART Async transmit 9 RB3 Digital Output PWM Fan 10 RB4 11 RB5 12 RB6 13 RB7 5 GND 14 5v

FIG. 5 is a schematic of controller 32 for the control of two air chamber system as described above, with a common room temperature sensor for both air chambers and separate PWM output drivers for each fan 22 and 22B.

Pinouts for the PIC16F1827 microcontroller depicted in FIG. 5 for the control of a dual air chamber system with separate PWM output drivers for each fan 22 and 22B are:

Pin Name Analog or Digital Direction Connection 17 RA0 Digital Output LED status indicator 18 RA1 Analog Input Inlet temperature sensor 1 1 RA2 Analog Input Outlet temperature sensor 1 2 RA3 Analog Input Room temperature sensor 3 RA4 Analog Input Inlet temperature sensor 2 4 RA5 15 RA6 Digital Output Fan 2 power on/off 16 RA7 Digital Output PWM Fan 2 6 RB0 Digital Output Fan 1 power on/off 7 RB1 Reserved for USART 8 RB2 Digital Output USART Async transmit 9 RB3 Digital Output PWM Fan 1 10 RB4 Analog Input Outlet temperature sensor 2 11 RB5 12 RB6 13 RB7 5 GND 14 5v

FIG. 6 is a schematic of controller 32 for the control of a two air chamber system with a common room temperature sensor for both air chambers. In this configuration, if both actual fan speeds are zero then both fans 22 and 22B will be off, if one fan speed is zero then the other fan will run normally as described herein, if both fan speeds are non-zero then both fans will run at the slower of the actual fan speeds and both the actual fan speeds will be set to the slower of the actual fan speeds accordingly. Pinouts for the PIC16F1826 microcontroller as depicted in FIG. 6 for the control of such a dual air chamber system.

Pin Name Analog or Digital Direction Connection 17 RA0 Digital Output LED status indicator 18 RA1 Analog Input Inlet temperature sensor 1 1 RA2 Analog Input Outlet temperature sensor 1 2 RA3 Analog Input Room temperature sensor 3 RA4 Analog Input Inlet temperature sensor 2 4 RA5 15 RA6 Digital Output Fan 2 power on/off 16 RA7 6 RB0 Digital Output Fan 1 power on/off 7 RB1 Reserved for USART 8 RB2 Digital Output USART Async transmit 9 RB3 Digital Output PWM Fan 1 10 RB4 Analog Input Outlet temperature sensor 2 11 RB5 Digital Output PWM Fan 2 (steered) 12 RB6 13 RB7 5 GND 14 5v

Controller 32 performs an analog to digital conversion of the voltage level running through each particular temperature sensor to generate an associated digital signal representative of the associated temperature value. At each such instance, controller 32 may perform checks to determine whether the particular temperature sensor has developed either an open circuit or short circuit fault. If any such fault is detected, controller 32 will signal a fault by illuminating a light emitting diode or other light emitting device, such as a incandescent lamp, generating a message on a screen, sending a text message, or email message, emitting a sound, or may signal the fault by some other method that can be selected by a person of ordinary skill in the art. Controller 32 may be programmed or configured by a person of ordinary skill in the art to signal a fault with a unique signal using one or more of the above signal generating means.

Controller 32 can be configured to also shut down fan 22 upon detection of such a fault. If controller 32 is configured to control more than one air heater, then controller 32 may be configured to alert such a fault in such a manner to identify the associated air heater where such fault applies. Further, controller 32 may be configured to only shut down the fan 22 or fan 22B associated with the air heater with the associated fault.

Controller 32 may be mounted within an enclosure. A temperature sensor may be located within the enclosure of controller 32. Room temperature sensor 28 may be located within enclosure of controller 32. Heat and lack of air circulation may result in room temperature sensor 28 identifying a room temperature value that is greater than the actual room temperature value. Controller 32 may be programmed and configured by a person of ordinary skill in the art to adjust for this temperature offset, which may be constant, or may be dependent on other measurable factors such as the duration controller 32 has been powered on, for example.

If the room temperature sensor 28 is located within the enclosure of controller 32, it may be used to detect if controller 32 electronics are operating at a temperature greater than desired, such as in an overheating situation. Room temperature sensor 28 may detect a room temperature value that exceeds a programmed or configured threshold, set to be indicative of an overheating situation. If room temperature sensor 28 senses a room temperature value that exceeds the associated overheating threshold, then controller 32 may be programmed or configured to shut down all controlled fans and to then shut itself down, or reduce processing until such time that the room temperature value has dropped back below the overheating threshold, or another programmed or configured value, for example a resume operation value, where such resume operation value may be less than the overheating threshold.

Controller 32 may also be programmed or configured by a person of ordinary skill in the art to indicate normal operation or ready mode upon startup by issuing a unique signal using one or more of the above signal generating means.

Controller 32 may further include means for data logging or data communication. For example, controller 32 may be configured to, at a predetermined or configured time interval, broadcast readings on a EUSART line, or similar line, or by other means that can be intercepted by such device as a line driver or controller configured to receive such readings data for transmission to a computer for data logging, storage, display, manipulation, and analysis. The broadcast data may include such values as temperature sensor values (actual temperature values or digital representations of voltages or resistances across such sensors), fan speeds, error codes, duration values that signify how long the controller 32 has been active, fan acceleration value, for example. Such data can be used to graph operation of the system and, or, provide methods of evaluating efficiency of the system, running costs and comparative cost savings (for example against the cost of an electrically powered heater with heating element or motor and heating element that provides a similar output to that of a solar collector).

The headings and Abstract provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

The present disclosure discusses air heater systems and control methods. A person of ordinary skill in the art will recognize that the disclosed embodiments could be implemented with single air chamber systems, or multi air chamber systems, with any number of inlets, outlets, a shared room temperature sensor or room temperature sensors for each unit, for example.

The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Although specific embodiments of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be recognized by those skilled in the relevant art. The teachings provided herein of the various embodiments can be applied to other fiber reinforced materials, not necessarily the exemplary methods and apparatus generally described above. For example, the various embodiments described above can be combined to provide further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure. 

1. A method for controlling an air heating system, the air heating system for heating air in a room, the air heating system comprising an air chamber, an inlet coupling the room to the air chamber to allow the passage of air from the room into the air chamber, an outlet coupling the air chamber to the room to allow the passage of air from the air chamber to the room, a fan for motivating air to pass from the room to the air chamber and back into the room, an inlet temperature sensor which yields an inlet temperature value, an outlet temperature sensor which yields an outlet temperature value, a room temperature sensor which yields a room temperature value, and a controller, the controller having data storage for storage of a minimum fan speed value, a fan start threshold value, a fan timer value, a full fan speed value, and a maximum fan speed value, wherein the controller is adapted to control speed of the fan, the method comprising: determining if the inlet temperature value is greater than the fan start threshold value, and if so setting the fan to run for the duration of the fan timer value at at least the minimum fan speed.
 2. The method of claim 1 wherein the controller data storage further comprises a temperature gradient value, and wherein the method further comprises determining if the outlet temperature value is greater than the room temperature and if so, further determining if the outlet temperature value is greater than the inlet temperature value by the temperature gradient value, and if so, setting the fan to run at a speed dependent on the outlet temperature value, greater than or equal to the minimum fan speed value and less than the maximum fan speed value.
 3. The method of claim 1 wherein the controller data storage further comprises a fan acceleration value and wherein the method further comprises determining if the actual fan speed is less than the desired fan speed and if not, then setting the actual fan speed to the desired fan speed and reducing the fan acceleration value, and if the actual fan speed is less than the desired fan speed, increasing the actual fan speed by the fan acceleration value and if the actual fan speed then is equal to the desired fan speed, then increasing the fan acceleration value.
 4. The method of claim 1 further comprising determining if the outlet temperature value is greater than or equal to the full fan speed value and if so, setting the fan to run at the maximum fan speed value.
 5. The method of claim 2 wherein if the fan timer value is exceeded, and if the outlet temperature value is not greater than the inlet temperature value by the temperature gradient value, then shutting down the fan.
 6. An air heating system for heating air in a room, the air heating system comprising an air chamber, an inlet coupling the room to the air chamber to allow the passage of air from the room into the air chamber, an outlet coupling the air chamber to the room to allow the passage of air from the air chamber to the room, a variable speed fan for motivating air to pass from the room to the air chamber and back into the room, an inlet temperature sensor which yields an inlet temperature value, an outlet temperature sensor which yields an outlet temperature value, a room temperature sensor which yields a room temperature value, and a controller for controlling the speed of the fan wherein the controller is adapted to control the speed of the fan based on at least one of the inlet temperature value, the outlet temperature value, and the room temperature value.
 7. The air heating system of claim 6 wherein room further comprises a floor and a ceiling and wherein the outlet is positioned closer to the floor than the inlet.
 8. An air heating system for heating air in a room, the air heating system comprising a first air chamber, a first inlet coupling the room to the first air chamber to allow the passage of air from the room into the first air chamber, a first outlet coupling the first air chamber to the room to allow the passage of air from the first air chamber to the room, a first variable speed fan for motivating air to pass from the room to the first air chamber and back into the room, a first inlet temperature sensor which yields a first inlet temperature value, a first outlet temperature sensor which yields a first outlet temperature value, a room temperature sensor which yields a room temperature value, a second air chamber, a second inlet coupling the room to the second air chamber to allow the passage of air from the room into the second air chamber, a second outlet coupling the second air chamber to the room to allow the passage of air from the second air chamber to the room, a second variable speed fan for motivating air to pass from the room to the second air chamber and back into the room, a second inlet temperature sensor which yields a second inlet temperature value, a second outlet temperature sensor which yields a second outlet temperature value, and a controller informationally coupled to each of the first inlet temperature sensor, to pass the first inlet temperature value from the first inlet temperature sensor to the controller, the first outlet temperature sensor, to pass the first outlet temperature value from the first outlet temperature sensor to the controller, the second inlet temperature sensor, to pass the second inlet temperature value from the second inlet temperature sensor to the controller, the second outlet temperature sensor, to pass the second outlet temperature value from the second outlet temperature sensor to the controller, the room temperature sensor to pass the room temperature value from the room temperature sensor to the controller, wherein the controller is adapted to control the speed of the first fan based on at least one of the first inlet temperature value, the first outlet temperature value, and the room temperature value, and to control the speed of the second fan based on at least one of the second inlet temperature value, the second outlet temperature value, and the room temperature value.
 9. The air heating system of claim 8 wherein room further comprises a floor and a ceiling and wherein at least one of the first outlet and second outlet is positioned closer to the floor than at least one of the first inlet and second inlet.
 10. The air heating system of claim 8 wherein the controller is further adapted to control the speed of the first fan based on at least one of the second inlet temperature value, and the second outlet temperature value, and to control the speed of the second fan based on at least one of the first inlet temperature value, and the first outlet temperature value.
 11. An air heating system for heating air in a room, the air heating system comprising a first air chamber, a first inlet coupling the room to the first air chamber to allow the passage of air from the room into the first air chamber, a first outlet coupling the first air chamber to the room to allow the passage of air from the first air chamber to the room, a first variable speed fan for motivating air to pass from the room to the first air chamber and back into the room, a first inlet temperature sensor which yields a first inlet temperature value, a first outlet temperature sensor which yields a first outlet temperature value, a first room temperature sensor which yields a first room temperature value at a first room location, a second air chamber, a second inlet coupling the room to the second air chamber to allow the passage of air from the room into the second air chamber, a second outlet coupling the second air chamber to the room to allow the passage of air from the second air chamber to the room, a second variable speed fan for motivating air to pass from the room to the second air chamber and back into the room, a second inlet temperature sensor which yields a second inlet temperature value, a second outlet temperature sensor which yields a second outlet temperature value, and a second room temperature sensor which yields a second room temperature value at a second room location, and a controller informationally coupled to each of the first inlet temperature sensor, to pass the first inlet temperature value from the first inlet temperature sensor to the controller, the first outlet temperature sensor, to pass the first outlet temperature value from the first outlet temperature sensor to the controller, the second inlet temperature sensor, to pass the second inlet temperature value from the second inlet temperature sensor to the controller, the second outlet temperature sensor, to pass the second outlet temperature value from the second outlet temperature sensor to the controller, the first room temperature sensor to pass the first room temperature value from the first room temperature sensor to the controller, the second room temperature sensor to pass the second room temperature value from the second room temperature sensor to the controller, wherein the controller is adapted to control the speed of the first fan based on at least one of the first inlet temperature value, the first outlet temperature value, and the first room temperature value, and to control the speed of the second fan based on at least one of the second inlet temperature value, the second outlet temperature value, and the second room temperature value.
 12. An air heating system for heating air in a room, the air heating system comprising a first air chamber, a first inlet coupling the room to the first air chamber to allow the passage of air from the room into the first air chamber, a first outlet coupling the first air chamber to the room to allow the passage of air from the first air chamber to the room, a first variable speed fan for motivating air to pass from the room to the first air chamber and back into the room, a first inlet temperature sensor which yields a first inlet temperature value, a first outlet temperature sensor which yields a first outlet temperature value, a room temperature sensor which yields a room temperature value, a second air chamber, a second inlet coupling the room to the second air chamber to allow the passage of air from the room into the second air chamber, a second outlet coupling the second air chamber to the room to allow the passage of air from the second air chamber to the room, a second variable speed fan for motivating air to pass from the room to the second air chamber and back into the room, a second inlet temperature sensor which yields a second inlet temperature value, a second outlet temperature sensor which yields a second outlet temperature value, and a controller informationally coupled to each of the first inlet temperature sensor, to pass the first inlet temperature value from the first inlet temperature sensor to the controller, the first outlet temperature sensor, to pass the first outlet temperature value from the first outlet temperature sensor to the controller, the second inlet temperature sensor, to pass the second inlet temperature value from the second inlet temperature sensor to the controller, the second outlet temperature sensor, to pass the second outlet temperature value from the second outlet temperature sensor to the controller, the room temperature sensor to pass the room temperature value from the room temperature sensor to the controller, wherein the controller is adapted to control the speed of the first fan based on at least one of the first inlet temperature value, the first outlet temperature value, and the room temperature value, and to control the speed of the second fan based on at least one of the second inlet temperature value, the second outlet temperature value, and the room temperature value. 